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Combinatorial selection of molecular conformations and supramolecular synthons in quercetin cocrystal landscapes: a route to ternary solids.

Dubey R, Desiraju GR - IUCrJ (2015)

Bottom Line: The crystallization of 28 binary and ternary cocrystals of quercetin with dibasic coformers is analyzed in terms of a combinatorial selection from a solution of preferred molecular conformations and supramolecular synthons.Variability in molecular conformation and synthon structure led to an increase in the energetic and structural space around the crystallization event.In the landscape context, we develop a strategy for the isolation of ternary cocrystals with the use of auxiliary template molecules to reduce the molecular and supramolecular 'confusion' that is inherent in a molecule like quercetin.

View Article: PubMed Central - HTML - PubMed

Affiliation: Solid State and Structural Chemistry Unit, Indian Institute of Science , Bangalore 560 012, India.

ABSTRACT
The crystallization of 28 binary and ternary cocrystals of quercetin with dibasic coformers is analyzed in terms of a combinatorial selection from a solution of preferred molecular conformations and supramolecular synthons. The crystal structures are characterized by distinctive O-H⋯N and O-H⋯O based synthons and are classified as nonporous, porous and helical. Variability in molecular conformation and synthon structure led to an increase in the energetic and structural space around the crystallization event. This space is the crystal structure landscape of the compound and is explored by fine-tuning the experimental conditions of crystallization. In the landscape context, we develop a strategy for the isolation of ternary cocrystals with the use of auxiliary template molecules to reduce the molecular and supramolecular 'confusion' that is inherent in a molecule like quercetin. The absence of concomitant polymorphism in this study highlights the selectivity in conformation and synthon choice from the virtual combinatorial library in solution.

No MeSH data available.


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Selection of molecular conformation, Conf 2A, and supramolecular synthon, synthon I, in the anhydrous 2:3 QUE:PHE crystal structure.
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fig6: Selection of molecular conformation, Conf 2A, and supramolecular synthon, synthon I, in the anhydrous 2:3 QUE:PHE crystal structure.

Mentions: Finally, the quercetin–phenazine cocrystal landscape (QUE:PHE) is very comparable and has five crystal forms: two anhydrates, a methanolate, a 1,4-dioxane solvate and a monohydrate. Of these crystal forms, two are porous with Conf 5B and synthon E and their one-directional porous channel is occupied by 1,4-dioxane and PHE as a guest molecule. In the methanolate, Conf 6B is taken with synthon D. PHE is geometrically different from DPE-I and DPE-II, but it still amplifies Conf 7B in the monohydrate; this conformation is favored by DPE-I and DPE-II in their helical structures. However, in the case of the QUE–PHE landscape the rigid nature of the small coformer molecule PHE prevents adoption of the helical structure for the monohydrate. The observed structure is nonporous with an alternative supramolecular synthon, synthon G. The final structure is the second anhydrate where the hitherto virtual conformation Conf 2A is expressed as also synthon I that had not been observed previously (Fig. 6 ▸). These unique selections of conformation and supramolecular synthons highlight the virtuality of conformational and synthon libraries in supersaturated solution that could selectively be fine-tuned by experimental conditions. So, in general, the QUE:PHE cocrystal landscape shows the same conformations selection: Conf 6B, Conf 5B and Conf 7B as in the previous landscapes. These conformations lead respectively to each of the three structure types: nonporous, porous and helical.


Combinatorial selection of molecular conformations and supramolecular synthons in quercetin cocrystal landscapes: a route to ternary solids.

Dubey R, Desiraju GR - IUCrJ (2015)

Selection of molecular conformation, Conf 2A, and supramolecular synthon, synthon I, in the anhydrous 2:3 QUE:PHE crystal structure.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4491312&req=5

fig6: Selection of molecular conformation, Conf 2A, and supramolecular synthon, synthon I, in the anhydrous 2:3 QUE:PHE crystal structure.
Mentions: Finally, the quercetin–phenazine cocrystal landscape (QUE:PHE) is very comparable and has five crystal forms: two anhydrates, a methanolate, a 1,4-dioxane solvate and a monohydrate. Of these crystal forms, two are porous with Conf 5B and synthon E and their one-directional porous channel is occupied by 1,4-dioxane and PHE as a guest molecule. In the methanolate, Conf 6B is taken with synthon D. PHE is geometrically different from DPE-I and DPE-II, but it still amplifies Conf 7B in the monohydrate; this conformation is favored by DPE-I and DPE-II in their helical structures. However, in the case of the QUE–PHE landscape the rigid nature of the small coformer molecule PHE prevents adoption of the helical structure for the monohydrate. The observed structure is nonporous with an alternative supramolecular synthon, synthon G. The final structure is the second anhydrate where the hitherto virtual conformation Conf 2A is expressed as also synthon I that had not been observed previously (Fig. 6 ▸). These unique selections of conformation and supramolecular synthons highlight the virtuality of conformational and synthon libraries in supersaturated solution that could selectively be fine-tuned by experimental conditions. So, in general, the QUE:PHE cocrystal landscape shows the same conformations selection: Conf 6B, Conf 5B and Conf 7B as in the previous landscapes. These conformations lead respectively to each of the three structure types: nonporous, porous and helical.

Bottom Line: The crystallization of 28 binary and ternary cocrystals of quercetin with dibasic coformers is analyzed in terms of a combinatorial selection from a solution of preferred molecular conformations and supramolecular synthons.Variability in molecular conformation and synthon structure led to an increase in the energetic and structural space around the crystallization event.In the landscape context, we develop a strategy for the isolation of ternary cocrystals with the use of auxiliary template molecules to reduce the molecular and supramolecular 'confusion' that is inherent in a molecule like quercetin.

View Article: PubMed Central - HTML - PubMed

Affiliation: Solid State and Structural Chemistry Unit, Indian Institute of Science , Bangalore 560 012, India.

ABSTRACT
The crystallization of 28 binary and ternary cocrystals of quercetin with dibasic coformers is analyzed in terms of a combinatorial selection from a solution of preferred molecular conformations and supramolecular synthons. The crystal structures are characterized by distinctive O-H⋯N and O-H⋯O based synthons and are classified as nonporous, porous and helical. Variability in molecular conformation and synthon structure led to an increase in the energetic and structural space around the crystallization event. This space is the crystal structure landscape of the compound and is explored by fine-tuning the experimental conditions of crystallization. In the landscape context, we develop a strategy for the isolation of ternary cocrystals with the use of auxiliary template molecules to reduce the molecular and supramolecular 'confusion' that is inherent in a molecule like quercetin. The absence of concomitant polymorphism in this study highlights the selectivity in conformation and synthon choice from the virtual combinatorial library in solution.

No MeSH data available.


Related in: MedlinePlus